In the manufacture of CO.sub.2 snow, the use of snow horns or the like, with multiple nozzles for injecting liquid CO.sub.2 (LCO.sub.2) into a snow chamber for increased production, is well-known practice. In general, the pressurized LCO.sub.2 may be directed into the snow chamber or horn along or at various acute angles to the vertical center line of the horn to form CO.sub.2 snow during the expansion and vaporization phase. In the conversion, the snow-vapor mixture, especially where several nozzles are used, acquires a large amount of kinetic energy. This results in high velocities and turbulence of the mixtures wich tend to cause snow "sticking" due to impact of snow particles on adjacent walls of the horn; also, irregular distribution of the snow takes place at the horn exhaust.
For overcoming these problems, various methods and devices have been employed for reducing mixture velocities, such as diffusion, abrupt expansion, directional change, etc.; however, these devices have not been entirely satisfactory as the solid snow particles do not follow the law of gases and generally retain a significant part of their kinetic energy. In other words, solid particles of CO.sub.2 continue to move at comparatively high velocities so as to impact on adjacent walls; thus, there is a tendency for the snow to accumulate on the walls while passing through the snow horn.
Accordingly, the present invention is concerned with overcoming the problems referred to above, particularly as to turbulence and high velocities of the snow-vapor mixtures within the snow chamber, so that CO.sub.2 snow can be produced at a uniform and even rate and without significant sticking on the snow horn walls.